The invention relates to data communications, and more specifically to method and apparatus for processing call progress of a serial communication device.
Modern modems are used to connect PCs, or other data terminal equipment (DTE), into wide area communication networks, in which the telephone system is used to carry information from one PC to another. Over the years many communication standards have been developed, enabling a standards-compliant modem made by one manufacturer to communicate with a standards-compliant modem made by another manufacturer. These protocols specify various aspects of a communication protocol, such as signal constellations and coding methods to be used under the standard.
To date, modems have been typically implemented with an on-board speaker to play call progress data during a call progress period. Alternatively a modem typically includes a special cable connecting with an audio system of a host, such that the call progress signal may be transmitted from the modem to the host and be played at the audio system of the host, through the special cable. FIG. 1A shows a conventional modem having an onboard speaker to play the call progress signal. The system 100 typically includes a host 101 coupled with a modem device 102 through a serial interface 103. The modem device 102 typically includes an onboard speaker 109. Thus, during a call progress period, call progress signal received from the outside phone line 107, is extracted from the data access arrangement (DAA) 106. The DAA 106 then transmits the call progress signal to the onboard speaker 109 through an amplifier 108.
Alternatively, as described in FIG. 1B, a modem may utilize an audio system of the host 101 to play call progress. Referring FIG. 1B, the call progress signal received from the phone line 107 is extracted from the DAA 106. The DAA 106 then transmits the call progress signal to an audio output circuit 110. The audio output circuit 110 then transmits the call progress signal through an audio cable 115 to an audio input circuit 111 of the host 101. A typical mixer circuit 112 then mixes the call progress signal with other audio inputs (e.g., music data played from an application of the host) and inputs the call progress signal to the audio system 113. The call progress signal is then played at the speaker 114 of the host.
As described above, a conventional modem requires either a speaker built-in on the modem to play call progress, or a special circuitry such as, audio output circuit 110, audio input circuit 111, to utilize the audio system of the host. In a competitive market, sometimes the costs of these components or circuits are not acceptable. Hence, it is desirable to have an improved method or system such that a modem may utilize the audio system of the host without extra costs.
Accordingly, the present invention introduces a method and system to provide the capability of a serial based analog modem to play its connection call progress in a digital format, thus eliminating the need for analog to digital conversion at the host and the extra circuitry. In one aspect of the invention, an exemplary method includes receiving data at the serial communication device, from a serial communication network; identifying the data as call progress audio samples; transmitting the call progress audio samples to the host through the serial interface, the serial interface carrying serial data or call progress audio samples; and playing the call progress audio samples at the audio system of the host.
In an alternative embodiment, the exemplary method further includes receiving the data at the host, the data being transmitted from the serial communication device through the serial interface; examining the data at the host, to determine whether the data are call progress audio samples; transmitting the audio samples to the audio system and playing the audio samples at the audio system, if the data are call progress audio samples; and processing the data as regular serial data at the host, if the data are not call progress audio samples.
In yet another alternative embodiment, an exemplary method includes receiving data at the serial communication device, from a serial communication network, identifying the data as call progress audio samples; transmitting a first character sequence to the host through the serial interface, the first character sequence identifying starting of the call progress; transmitting the call progress audio samples to the host through the serial interface, the serial interface carrying serial data or call progress audio samples; and transmitting a second character sequence to the host through the serial interface, the second character sequence indicating ending of the call progress.
In yet another alternative embodiment, an exemplary method includes receiving the data at the host, the data being transmitted from the serial communication device through the serial interface, the serial interface carrying serial data or call progress audio samples; examining the data at the host, to determine whether the data are call progress audio samples; transmitting the audio samples to the audio system and playing the audio samples at the audio system, if the data are call progress audio samples; and processing the data as regular serial data at the host, if the data are not call progress audio samples.